I remember The McCoy's Hang On Sloopy being a big hit in the Fall of 1965. It predated Bubblegum though. Rick Derringer and The McCoy's recorded the vocals to the instrumental track recorded by an Australian group called The Strangeloves (who were really from New York). The lyrics were a bit provocative and not aimed at kids just like those of Gloria recorded by Van Morrison and Them a year before. Gloria was banned on some radio stations...

To my ears, there was also a large overlap between Bubblegum and One-Hit-Wonders. What do you think?

60's: Green Tambourine (Lemon Pipers), Judy In Disguise (John Fred and his Playboy Band), I Had Too Much to Dream Last Night (Electric Prunes), Na Na Hey Hey Kiss Him Goodbye (Steam), More Today than Yesterday (Spiral Staircase), Smile a Little Smile for Me (Flying Machine), In the Year 2525 (Zager and Evans), Israelites (Desmond Decker and the Aces), Love Can Make You Happy (Mercy)